Understanding this gradient helps narrow down species possibilities. A fish spotted in Indonesia may have a closely related, look-alike cousin in French Polynesia, or it may not exist there at all. 2. Key Reef Creature Categories

Where exactly on the reef is it located? Crest, flat, drop-off, or symbiotic with another species?

When observing a creature underwater, note these four diagnostic characteristics before checking a reference manual:

: "AIMS Coral Finder PDF" or "AIMS reef monitoring field guide"

Best for: Overall ecosystem understanding and species density.

White-tip and black-tip reef sharks are common.

Understanding the substrate of the reef is key to understanding the ecosystem.